1. Field of the Invention
The present invention generally relates to solid state energy detectors and, in particular, to such detectors which combine the detection of more than one energy mode.
2. Statement of the Prior Art
For some time there has been an interest in having an imaging apparatus which is capable of simultaneously or alternatively acquiring images using both millimeter wave and infrared energy. While millimeter wave, MMW, energy, as found in radar systems, is more effective than infrared IR, over long distance and in adverse weather conditions, IR energy provides greater resolution. Thus, the hope of combining these techniques into a single device is to achieve the advantages of both techniques. Numerous devices have been developed which attempt to integrate both MMW and IR sensors into the same device. Such devices usually use the same energy collection portal and then direct the different types of energy to separate and different sensing devices using complex optical arrangements. Disadvantageously, this approach cannot be used for manufacturing high density arrays and suffers from difficult problems in combining the data from the separate sensors, a process known as data fusion.
Although integrated circuit construction techniques have been used for some time to produce MMW antennas as integrated circuit conductors on semiconductor substrates, it has only been recently that IR sensors have been constructed using semiconductors and integrated circuit construction techniques. Nonetheless, the development of semiconductor IR sensors has progressed in such forms as HgCdTe detectors, quantum well infrared photodetectors (QWIPs) and infrared hot-electron transistors (IHETs).
A related development has been the combination of such semiconductor IR sensors with the advanced optical techniques of microlenses. Each IR pixel element in an array is associated with its own microlens which allows the size of the pixel element to be reduced while maintaining the area of incident IR energy via the microlens. The microlens concentrates the incident photons to a smaller area thus reducing the required detector area and volume.